BRUSSELS (Reuters) - The European Union said on Saturday it was concerned about alleged irregularities and a lack of transparency in Zimbabwe's election, its strongest criticism so far of a poll that Prime Minister Morgan Tsvangirai has branded a "farce".

The EU's verdict on the fairness of the elections will be crucial to deciding whether it continues to ease sanctions on the southern African country.

"The EU is concerned about alleged irregularities and reports of incomplete participation, as well as the identified weaknesses in the electoral process and a lack of transparency. The EU will continue to follow developments and work closely with its international partners in the weeks to come," EU foreign policy chief Catherine Ashton said in a declaration issued on behalf of the 28-nation bloc.